150 watt 12v heater

First I'm sorry if this question has been asked before. I looked and could not find it.

I should be adopting my 2014 550 classic next week and I'm wondering if a 150 watt electric car heater would work at heating the cabin down to 32f and how quickly would it drain the battery.

 

http://www.campinnforum.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=24453&Searchpage=8&Main=2573&Words=12+volt+heater&Search=true#Post24453